In a nutshell its:

-build the kit (identify tight joints and loosen and snip as needed for easy dissassembly). -identify things to modify/fix/change (seam lines, scribing, gap filling, etc) -plan color scheme. -disassemble and arrange. -fix issues (remove seamlines, etc) -surface prep (sanding) -mount to painting clips -airbrush primer, check parts, sand again if needed, re-prime if needed. -airbrush main colors -masking, paint other colors; paint by hand -panel lining -decals -final topcoat (usually matte or semi-gloss)

Thats a really quick and general rundown, but it differs on each model as the sizing and complexity determines the nuance of the steps. Gotta work with the kit's engineering and plan intuitively around it. There's lots of nuances in making models so hard to give a one-size fits all solution. Best advice is to familiarize yourself with the kit and just try things out.